NMR tomography particularly utilizing the projection-reconstruction imaging technique is well-known. In such a technique, a series of free induction decays (FID) is obtained usually with a suitable rf pulse sequence, while a magnetic field gradient is rotated through a number of angles in the image plane (which is assumed to be established by known means), each angular position corresponding to a given FID. The resulting FIDs are then Fourier transformed to yield a series of projections used to reconstruct the image. A difficulty with the foregoing method is that the field gradient necessarily causes broadening of particular chemical shifts in the image of the specimen slice, so that in a typical image of a specimen slice, particularly with biological specimens such as the human body, the various chemical shifts are not resolved, as the separations between the resonances are less than the broadening produced by the gradient in each projection. Methods have been suggested by Bendel et al in J. Magn. Reson., 38 343 (1980) and by Lauterbur et al in J. Amer. Chem. Soc., 97, 6866 (1975) which involve selective excitation or signal subtraction techniques which are not particularly applicable for complex systems, and require prior knowledge of the type of spectrum to be produced by the sample. In addition, a `sensitive-point` method of obtaining spectra of individual points is known, but such involves acquiring data separately from a large number of points and hence is a relatively time consuming method. Other methods are known in NMR imaging which involve emphasizing T.sub.2 (spin-spin relaxation) differences, and T.sub.1 (spin-lattice relaxation) differences. However, these methods do not produce actual spectra of any given points or area in the image of the specimen slice.